I'd like to share the ongoing results from a project that I've just embarked on from my Bortle 8/9 backyard. My goal is to obtain short (i.e. 15minute) fully calibrated (flats and darks 60 each) live stacks every night and then to double stack them in DSS as if they were single long-exposure lights. I aim to construct and HO (one-shot hydrogen/oxygen) RGB image of the Heart Nebula using this approach.

So far, over the past two nights, I managed to stack 496 frames for HO, in live stack batches of 30 frames each, yielding a total of 16 stacks. Each stack of 30 frames included exposures of 30 seconds, with a gain of 230 and an offset of 100. A peculiar feature in sharpcap when enabling auto-save every 15 minutes was that it stacked a 31st frame rendering a stack time of 15 minutes 30s.

I used FWHM filter at 5.30 and auto-brightness filter to reject outlier frames due to bad tracking or clouds and the stacking algorithm was set at sigma clipping with parameters adjusted to reject no more than 0.1% pixels in each frame.

The 16 stacks were then double stacked in DSS using median kappa sigma clipping with a threshold set to 3 and 30 iterations. I then used Photoshop to stretch and do some basic processing.

The canon lens was stepped down to f/5.45 using front-loaded step down filter rings with an effective front aperture of 55mm instead of the native 75mm.

So far I really like what I'm getting, here is the link to the (unpublished work-in-progress) image:

Forgot to mention that I used both the smart histogram tool followed by manual fine-tuning and visual confirmation to get the histogram I thought was best for the stack. I forgot to save an individual frame to share its FITS Liberator image here, I'll do that on the next run.

I wanted to also add that I chose to go for high gain of 230 to improve (lessen) quantization error. Any loss in DR would be recovered when doublestacking many stacks.

Furthermore, each stack upon completion and auto-save and reset, was manually triggered to dither in PHD2 by 15 pixels on the imaging scale before starting a new stack. This was to benefit the stacking algorithm in DSS. Individual frames going into the 15 minute live stack were not dithered, but guided.

Excellent work, Minos! It is amazing what can be done in light-polluted environments. I can't wait for the colorized version! Also, what's great about narrowband imaging is that it can be done while the Moon is up. We don't get that many clear nights in the NYC area, so narrowband is a great addition.

Brian - Yes, narrowband is a must for detail in such LP! RGB will be washed out in comparison. Still though, the HO data will serve as the detail in the Luminance

Dave - Yes, I too am pleased with the data distribution I wouldn't really want to disrupt the critter ecosystem running rampant in the plantlife and lawn in front of my backyard, they keep me company at night - haha, no really, the apartment complex is responsible for managing that, they also manage to turn the sprinklers on at 2am, so that's my curfew!

I've just restacked the 16 stacks using SC Live Stack again using folder monitor and the same settings as above. You can see the dithering was aggressive and causes you to sacrifice some fov and also causes the bumpy tail on the black end of the histogram. I'm processing it to the same level as the DSS stack to compare them.